Red Dead Redemption: Undead Nightmare Pack Q&A :

i completed every single mission and side mission and saved every town but i still cant get into mexico! there is no mission signs anywhere so i have no idea what the f*** to do so im basically stuck in New Austin and above. someone please help me!

Alright so i saved all the towns and beaten all the Question mark missions but i still cant get into mexico, plus it doesnt have any mission signs anywhere so im stuck in America.What do i do next to continue the game?